#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair < int, int > ii;

const int N = 1e6 + 5;
const int mod = 1e9 + 7;

int n, m;
int a[N], sum[N], dp[N], sumDp[N];

inline int add(int x, int y) {
	return x + y >= mod ? x + y - mod : x + y;
}

int main() {

	scanf("%d %d", &n, &m);

	for(int i = 1; i <= m; i++) {
		int x;
		scanf("%d", &x);
		a[x]++;
	}

	for(int i = 1; i <= n; i++)
		sum[i] = sum[i - 1] + a[i];

	dp[n + 1] = 1;

	int ans = 0;

	sumDp[n + 2] = 1;
	sumDp[n + 1] = 1;

	for(int i = n; i >= 1; i--) {
		if(!a[i-1])
		for(int j = i; j <= n; j++) {
			if(j - i + 1 == sum[j] - sum[i - 1] and !a[j + 1]) {
				dp[i] = add(dp[i], sumDp[j + 2]);
			}
		}
		if(a[i])
			ans = 0;
		ans = add(ans, dp[i]);

		if(a[i])
			sumDp[i] = dp[i];
		else
			sumDp[i] = add(sumDp[i + 1], dp[i]);
	}

	printf("%d\n", ans);

    return 0;

}